Publication Date:
1983-05-01
Description:
The geologic and geotechnical characteristics of thick soft Champlain Sea clay deposits at Hawkesbury, Ontario are presented in this paper. A second paper will deal with the mineralogy and geochemistry of the same deposits.A westerly clay plain at ~50 m and an easterly plain at ~75 m elevation occur in the area. Preconsolidation pressure versus depth curves obtained for clays from both deposits show marked preconsolidation near the top and bottom drainage boundaries and nearly normally consolidated conditions at the centre. This suggests that both sites were loaded by sandy fluvial (deltaic) sediments that were eroded ~70 years after deposition, an ancestral meander of the Ottawa River being responsible for the erosion on the lower clay plain. Two stratigraphic schemes compatible with the σP′ versus depth profiles are presented. For the lower elevation clay plain these schemes suggest erosion of 21 m of deltaic sands, a value generally confirmed by field studies of deltaic sand terraces to the west.The sensitivity of the lower level clays decreases from ~25 at surface to ~5 at depth. The upper level clays are very different, having a maximum sensitivity of ~20 at mid-depth and decreasing towards the top and bottom. These trends reflect differences in the liquidity index for both clays and in salinity for the lower level clays. The low values of sensitivity relate to the relatively high clay mineral content of 51% and salt content of 1–20 g/L measured on these partially "leached" clays. Keywords: Champlain clays, preconsolidation, diffusion, erosion, vane strength, salinity.
Print ISSN:
0008-3674
Electronic ISSN:
1208-6010
Topics:
Geosciences
Permalink
